Why does a gynecologist order a 17 alpha ohp test in a female?

Genetic disease hunt. Congenital adrenal hyperplasia is a family of several illnesses in which the adrenals can't make enough cortisol without being pushed hard and then make other hormone as by-products. In the two common ones, 17alpha hydroxyprogesterone is up, in another it's absent; they're quite common and manageable if diagnosed & will make your life better.